Week 12: The Ugi Synthesis Collaborative Project

The Ugi reactions are up and running.

The combinations we are investigating are:

students

Aldehyde

Amine

Carboxylic acid

isocyanide

8

3,4-dimethoxybenzaldehyde

methyl

amine

3,4,5-trihydroxybenzoic acid ●monohydrate

p-toluenesulfonyl

methyl isocyanide

5

3,4-dimethoxybenzaldehyde

methyl

amine

2,4,6-trihydroxybenzoic acid ●monohydrate

p-toluenesulfonyl

methyl isocyanide

5

3,5-dimethoxybenzaldehyde

methyl

amine

3,4,5-trihydroxybenzoic acid ●monohydrate

p-toluenesulfonyl

methyl isocyanide

5

3,5-dimethoxybenzaldehyde

methyl

amine

2,4,6-trihydroxybenzoic acid ●monohydrate

p-toluenesulfonyl

methyl isocyanide

 

The combinations with the gallic acid (3,4,5-trihydroxybenzoic acid) precipitated very quickly. I was a little alarmed about that so I instructed the Wednesday group to weigh out all their compounds first and then add them together sequentially as soon as the previous mixture was homogeneous. I noticed that in the Monday group sometimes students would take 10 minutes or more to locate the next reagent and weigh it out. As far as I can tell, that did not make much difference, but it is something to consider. We did not have any problems with solubility, other than a rather rapid onset of precipitation.

 

We doubled the amounts (1 mmole to 2 mmole) from what is typically done by the UsefulChem group. In my experience, it is always a good idea to give undergraduate students as much product as possible to play around with. With a group of students, anomalies always crop up. Some may be due simply to inattention (“human error” as my students report in their write-ups), others are more subtle and insidious. It is always a good idea to characterize all the reagents – they tend to pop up in student “products.” Its not hard to spot in the anomalous vials in our photos.

 

The second set of reagents corresponds to UsefulChem experiment 171H (Spreadsheet number: 171HV2B8) which have crystals for within 8-10 days.

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